Metabolic pathways and gene expression changes in Amblyseius orientalis Ehara (Acari: Phytoseiidae): The role of host plant nutrients in predator-pest dynamics

Amblyseius orientalis Ehara (Acari: Phytoseiidae) is one local predatory mite in China that has high potential for controlling Polyphagotarsonemus latus, a globally important pest to many vegetables and crops. To further evaluate the control potential of A. orientalis on different host plants against P. latus, we selected bean, cucumber, and pepper as host plants to feed P. latus, and then to feed A. orientalis. It was found when the prey P. latus fed on cucumber leaves, development of A. orientalis was the slowest, with the lowest egg production and overall poor biological performance. When A. orientalis was fed with prey hosted on cucumber and the other two plants, there were 119 differentially expressed organic compounds. The differentially metabolites were significantly enriched in the pentose phosphate pathway and carbon metabolism pathway. Further transcriptomic analysis of A. orientalis revealed 36 differentially expressed genes. Among these genes, 20 were annotated in 17 pathways in KEGG, with significant enrichment in hippo signaling pathway-fly and polysaccharide degradation pathways detected. These results indicate that the development and reproduction of A. orientalis are significantly poorer when feeding on P. latus, leading to a marked decline in amino acids, sugars, lipids, and organic compounds in A. orientalis. Additionally, there are 36 genes with consistently different expression patterns in A. orientalis when comparing cucumbers to the other two host plants. This study is an initial attempt to unravel the biological mechanisms of how nutritional substances might affect biology of natural enemies through the food chain.